The pharmaceutical companies estimate that up to 50,000 inhalers from the affected batches are experiencing the problems, which are related to the delivery mechanism for the medication.

The Acting Chief Health Officer of NSW, Tony Penna, said people who used the inhalers should check the batch number by removing the canister from the plastic tube, where they will find the batch number on the bottom of the canister label.

“If they identify that they have one of the affected inhalers, it can be returned to their pharmacy for a free replacement,” Dr Penna said. "Should people using the affected batches of Ventolin or Asmol inhalers experience a worsening of their asthma or have concerns about the use of their inhaler they are advised to seek immediate medical attention."

He said that due to limited access to medical services over the Christmas and New Years period, asthma sufferers and their carers should ensure they knew what medical services were available over the coming week.